1. Field of the Invention
The present invention relates to a structure of a mirror device of a single-lens reflex camera.
2. Description of the Related Art
A single-lens reflex camera is configured to take a picture based on an object beam incident from a taking lens and observe the object based on the object beam incident from the taking lens. The single-lens reflex camera is generally provided with a quick return mirror as a mirror device that temporally changes whether to direct the object beam from the taking lens to an image taking side such as a film or image pickup device side, or an observing side.
When the position of the quick return mirror is changed, the single-lens reflex camera may have a problem that the quick return mirror bounds by a shock and the bounding quick return mirror appears in a photograph. Furthermore, when the quick return mirror bounds, there may also be a problem that since the camera cannot catch up with high-speed mirror drive, continuous exposure performance cannot be sped up.
A common method for avoiding this problem is to provide a cushioning material at a positioning location of the quick return mirror and suppress bounding of the quick return mirror.
Many cameras released on the market in recent years have an auto-focus (AF) mechanism and a typical example of the AF mechanism provided for a single-lens reflex camera is a TTL phase contrast AF. A single-lens reflex camera capable of the TTL phase contrast AF generally has a structure as follows.
A part of a main mirror is configured as a semi-transmissive portion which is pivotable between a mirror down position where an object beam from a taking lens is reflected and a mirror up position retracted from the object beam. A sub-mirror for reflecting the object beam that has passed through the semi-transmissive portion at an observation position is provided on a rear side of the semi-transmissive portion and a distance measuring sensor for phase contrast AF is arranged on an optical path of the object beam reflected by the sub-mirror. When the main mirror is at the mirror up position, the sub-mirror is configured so as to be folded along the main mirror and retracted from the object beam.
As a technique of suppressing the bounding of the quick return mirror made up of the main mirror and sub-mirror, for example, Japanese Patent Application Laid-Open Publication No. 6-175223 discloses a technique of attracting the quick return mirror by a timing-controlled electromagnet.